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Question for Windell RE: LED Throwie Post

Forgive me if I'm completely missing it, but it seems like the comments section of this post has been closed.  

I have a dumb question, I'm not real familiar with electronics and power streams, but if I'm reading this right:

If the forward voltage of the LED is < 3v forward voltage, a resistor is going to bring it back into that 'completely safe, long-lasting' zone?

For reference, i'm planning on using throwies (possibly inside a ping pong ball as a diffuser) inside paper lamps at my wedding, for part of the centerpieces.  Thus, they only need to last about 12 hours, but the heat was the main concern.

So if i were using this purple LED i wouldn't need a resistor, and would still get the life I was hoping for, but using this yellow one, I would likely be better off with a 200ohm resistor in between the LED and battery, correct?

Thanks for your time, bookmarked the blog for future references, above and beyond this issue.


  • You are correct that the purple LED will not need a resistor, and that the yellow one would be better off with one.   Heat will not be an issue in any case.

    Also, you might be disappointed in the price/performance ratio of those radio shack LEDs. ;)
  • Yeah, just using radioshack as a test bed to get the bride (the one in charge) to make a choice (white lights in colored lanterns, or colored lights in white lanterns).  For the actual items, I'll buy them online.  In fact, I believe I'm going to start with this assorted pack from microtivity on amazon, it has the three colors we're interested in, as well as a ton of extras and resistors.

    Last question, (for now)... I could also put a 3-pin slide switch in to use as an on/off button on this, correct?  Rather than have to teach my aunts (who'll be setting up the venue that afternoon) how to make throwies?

    Thanks for the quick response.
  • Yes, you can add a slider switch, but it may be more complexity than it's worth.  Another good method is a "pull to activate" tab-- a piece of plastic that keeps the battery from making initial contact.
  • Eh, I've got 9 months to figure it out.  Always good to have a pile of switches around anyway.  

    Thanks again for the quick help, great site, will definitely be plugging it as I write more in my "how to be a groom" type blog.
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